<b>By Jodi Kendall</b> November 18, 2011

Sharks in Trouble

How Humans Are Far More Dangerous to Them Than They Are to Us

Sharks have been swimming in our seas for over 400 million years. And although they've been a top predator since before the time of dinosaurs, sharks are in critical danger of human exploitation. Of the 307 shark species currently reviewed by the International Union for Conservation of Nature (IUCN), 50 are threatened with extinction. Pelagic shark species are particularly vulnerable because country-specific legislation does not safeguard these fish on the high seas. Only three sharks—whale, white, and basking—are protected in international waters. Because of this reality, both direct and indirect catches of these apex predators are frequently unregulated, and global action is needed to protect all sharks in peril.

(See "The Health of the Ocean: What’s at Stake?")

There are several reasons for the sharp decline in worldwide shark populations. Fishing pressure is a primary cause, as sharks are hunted for their valuable fins, cartilage, organs, teeth, and skin. To supply the shark fin soup demand in Asian markets, fishermen will slice off a shark's fins and then discard the body in the water. While finning has been banned from most international waters, enforcement is lacking. Sharks can also become accidentally entangled in commercial fishing nets, even when they're not the intended target. It's estimated that as many as 73 million sharks are killed annually.

(Watch Video: "Torturing Sharks for Soup")

In addition to human exploitation, sharks grow slowly, reach maturity late in life, and give birth to relatively few pups, making it challenging for the species to recover from depleted populations. But sharks are vital to our marine ecosystems. As a top predator, sharks help keep prey populations in check and aquatic habitats healthy. Conservation groups are working to protect these fish by supporting international shark finning bans and legislation that reduces shark bycatch.

(See "Pacific Island Nations Take Lead in Shark Conservation.")

While sharks may have a fearsome reputation, it's largely unwarranted. Shark attacks are rare and often accidental. They're naturally curious, and many sharks live in the same warm water, coastal areas where humans like to swim, surf, and boat. It's possible that sharks can mistake a person for prey (like seals) and oftentimes attacks are merely a case of exploratory biting. People are much more likely to be struck by lightning than attacked by a shark, and 1,000 times more likely to be the victim of a dog bite.

(See "Shark Attack Facts.")

Mako Sharks
There are two kinds of mako sharks: shortfin and longfin. They are the largest, fastest open water sharks in the world, a species closely related to the great white. While makos share the same streamlined shaped body as their cousin, they are brilliant in color, with a metallic blue dorsal area and silvery-hued underbody. Unlike many other shark species, makos do not have serrated teeth—instead, they're pointed and razor-sharp, giving them the ability to slice through flesh with ease. It's believed that the shortfin mako shark was Ernest Hemingway's inspiration for the creature depicted in his beloved novel, The Old Man and the Sea.

Makos are able to regulate their body temperature, keeping themselves warmer than the surrounding waters. They're a large shark capable of growing to over eight feet in length. And since they're fast in the water—achieving speeds of over 20 miles per hour–makos can hunt a variety of large and agile prey, including tuna, billfish, swordfish, and blue sharks. Mako sharks are known to leap from the water and travel long distances at high speeds.

As makos are powerful, beautiful, aggressive, and swift, they've become an esteemed gamefish. The largest hooked mako on record weighed over a thousand pounds. But these sharks are highly vulnerable to fishing pressures, both direct (for their valuable fins, organs, and flavorful flesh) and indirect (as a byproduct catch of tuna and swordfish fisheries.)

(See "New Shark-Fin Pictures Reveal Ocean 'Strip Mining.'")

Blue Sharks
Like the mako, blue sharks are a pelagic species that rarely nears inshore areas. They prefer to patrol the seas from the surface to just over 1,000 feet in depth where they feed on squid, octopus, and small, bony fish. The blue shark has a slender body, large eyes, long snout, serrated teeth, and pointed pectoral fins. Their name comes from the striking indigo-blue coloring of their upper body. It's believed that this shark species can grow as big as 20 feet in length, but they're usually half that size.

Blue sharks can be potentially dangerous to humans and should be respected. They've been observed circling swimmers and divers for as long as 15 minutes, and are responsible for several attacks on shipwrecked sailors floating out at sea. But incidents are extremely rare, with only a dozen accounts on historical record.

Although blue sharks are commonly found in our oceans and grow more quickly than many other sharks, the species is currently listed as near threatened by the IUCN. These sharks are considered quite the gamefish by recreational anglers who appreciate the challenge of snagging one with light tackle. Commercial fishermen also catch blue sharks, either accidentally in their nets or directly for their valuable fins and body parts. It's estimated that up to 20 million blue sharks are killed each year, and worldwide populations have been unable to bounce back from these depletions. Because they're a migratory species, blue sharks would require global regulation to protect them in international waters.

Learn more about ocean overfishing and other issues being faced to protect the ocean.

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